#include<netinet/in.h>  // sockaddr_in  
#include<sys/types.h>   // socket  
#include<sys/socket.h>  // socket  
#include<stdio.h>       // printf  
#include<stdlib.h>      // exit  
#include<string.h>      // bzero  
  
#define SERVER_PORT 8000  
#define LENGTH_OF_LISTEN_QUEUE 20  
#define BUFFER_SIZE 1024  
#define FILE_NAME_MAX_SIZE 512  
  
int main(void)  
{  
    // 声明并初始化一个服务器端的socket地址结构  
    struct sockaddr_in server_addr;  
    bzero(&server_addr, sizeof(server_addr));  
    server_addr.sin_family = AF_INET;  
    server_addr.sin_addr.s_addr = htons(INADDR_ANY);  
    server_addr.sin_port = htons(SERVER_PORT);  
  
    // 创建socket，若成功，返回socket描述符  
    int server_socket_fd = socket(PF_INET, SOCK_STREAM, 0);  
    if(server_socket_fd < 0)  
    {  
        perror("Create Socket Failed:");  
        exit(1);  
    }  
    int opt = 1;  
    setsockopt(server_socket_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));  
  
    // 绑定socket和socket地址结构  
    if(-1 == (bind(server_socket_fd, (struct sockaddr*)&server_addr, sizeof(server_addr))))  
    {  
        perror("Server Bind Failed:");  
        exit(1);  
    }  
      
    // socket监听  
    if(-1 == (listen(server_socket_fd, LENGTH_OF_LISTEN_QUEUE)))  
    {  
        perror("Server Listen Failed:");  
        exit(1);  
    }  
  
    while(1)  
    {  
        // 定义客户端的socket地址结构  
        struct sockaddr_in client_addr;  
        socklen_t client_addr_length = sizeof(client_addr);  
  
        // 接受连接请求，返回一个新的socket(描述符)，这个新socket用于同连接的客户端通信  
        // accept函数会把连接到的客户端信息写到client_addr中  
        int new_server_socket_fd = accept(server_socket_fd, (struct sockaddr*)&client_addr, &client_addr_length);  
        if(new_server_socket_fd < 0)  
        {  
            perror("Server Accept Failed:");  
            break;  
        }  
  
        // recv函数接收数据到缓冲区buffer中  
        char buffer[BUFFER_SIZE];  
        bzero(buffer, BUFFER_SIZE);  
        if(recv(new_server_socket_fd, buffer, BUFFER_SIZE, 0) < 0)  
        {  
            perror("Server Recieve Data Failed:");  
            break;  
        }  
  
        // 然后从buffer(缓冲区)拷贝到file_name中  
        char file_name[FILE_NAME_MAX_SIZE+1];  
        bzero(file_name, FILE_NAME_MAX_SIZE+1);  
        strncpy(file_name, buffer, strlen(buffer)>FILE_NAME_MAX_SIZE?FILE_NAME_MAX_SIZE:strlen(buffer));  
        printf("%s\n", file_name);  
  
        // 打开文件并读取文件数据  
        FILE *fp = fopen(file_name, "r");  
        if(NULL == fp)  
        {  
            printf("File:%s Not Found\n", file_name);  
        }  
        else  
        {  
            bzero(buffer, BUFFER_SIZE);  
            int length = 0;  
            // 每读取一段数据，便将其发送给客户端，循环直到文件读完为止  
            while((length = fread(buffer, sizeof(char), BUFFER_SIZE, fp)) > 0)  
            {  
                if(send(new_server_socket_fd, buffer, length, 0) < 0)  
                {  
                    printf("Send File:%s Failed./n", file_name);  
                    break;  
                }  
                bzero(buffer, BUFFER_SIZE);  
            }  
  
            // 关闭文件  
            fclose(fp);  
            printf("File:%s Transfer Successful!\n", file_name);  
        }  
        // 关闭与客户端的连接  
        close(new_server_socket_fd);  
    }  
    // 关闭监听用的socket  
    close(server_socket_fd);  
    return 0;  
}  
